In the filtering of liquids to remove solids and, more generally particulates therefrom, for example the separation of solids from water in water-filtration systems, the separation of precipitates from chemical liquors, the separation of contaminant particles from oil (e.g. in the oil recirculation system of the automotive vehicle) and in other filtering applications it is known to provide a cylindrical filter body which is porous and is traversed by the liquid to be filtered (see German Gebrauchsmuster DT-Gbm 1 872 428). In this earlier system a cylindrical sintered body serves as the filter but is incapable of withstanding substantial tangential and radial stress so that it is not practical for use in systems in which a high-pressure differential is applied across the sintered body.
It has been proposed to increase the surface area of a filter of wire mesh, paper or fabric by folding same into a plurality of folds or corrugations. To date, however, this has not been applicable to sintered structures and such filters, because of the flexible material from which they are formed, also cannot withstand elevated pressures.
The advantages of sintered filters are numerous. For example, they may be made of sintered metal powders, sintered fibrous materials or sintered ceramics and thus may be designed to withstand a wide range of chemical attacks, high temperatures and other influences detrimental to conventional flexible folded filters.
However, until now the relative ratio of effective filtering surface area to volume or size of sintered filter bodies has been unsatisfactory, a disadvantage which together with the inability of conventional sintered filters to withstand high stresses, has limited the field of application for sintered filters.
Mention may be made of the well-known phenomenon in the structural arts that folded systems, i.e. ribbed or corrugated structures, e.g. of reinforced concrete have far greater strength than nonfolded structures (LUEGER, Lexikon DIE BAUTECHNIK, 1966, pages 416, 417). To date, however, these teachings have not influenced, to my knowledge, the design of filter cartridges.